If the URL in question appears in your timeline, it’ll cause the Twitter for iOS app to crash every time it’s opened. Users don’t even need to click on the link to be affected.
An example of a tweet that could cause the crash to occur is below; this is the tweet that Twitter for iOS to crash repetitively on my iPhone.
Punycode is a method in which Unicode characters — such as emoji — can be encoded for display in ASCII’s limited character set. The URL in question that’s circulating is a number of emoji’s translated using Punycode, according to @CPVideoMaker.
Naturally, when someone finds a bug that breaks something, everyone starts sharing it to mess with their followers.
Thousands of users on the social network poured onto the network via alternative apps to express their frustration that the official Twitter app for iOS seemingly wouldn’t open after encountering the Punycode tweet.
The bug doesn’t appear to affect third party apps or Twitter’s apps on other platforms. The company appears to be working around the bug by disabling individual links that use the method.
Update: Twitter’s iOS engineering lead just shared that the bug should be resolved now and that you should be able to launch the app again.